1. Field of the Invention
The present invention generally relates to radio transmissions and in particular to a radio transmission method and system having a high spectrum efficiency, evaluated in terms of transmission capacity of a radio channel.
2. Description of the Prior Art
As is known, radio transmissions are particularly attractive for their possibility of connecting two (or more) stations, spaced apart by large distances, without the need to lay cables or wires between the stations. Nevertheless, one of the limitations which affects such a type of transmission is the spectrum efficiency, evaluated in terms of transmission capacity of a radio channel, that is rather reduced. In order to increase the spectrum efficiency, several solutions, presently utilized, have been devised.
The classic solution consists in increasing the complexity of modulation in the transmission step. In other words, a higher number of symbols is transmitted and in this way it is as if the transmitted bit/sec were increased.
An alternative solution, which is also utilizable in association with the classic solution, consists in the so-called “frequency re-use”. The known types of frequency reuse systems are: spatial frequency reuse; polar frequency reuse and angle frequency reuse.